New Mechanics the Raiding Tiers introduced since Classic

NOTE: This list is just meant for entertainment purposes and people who might find it interesting. I wrote it in quite a short time with only using my own memories and my own opionion after being a Hardcore/Semi Hardcore raider since 2005. So if there is a mistake somewhere or someone thinks he knows better, then you may of course discuss about it but please no "xy isnt true you are so f****** stupid" (bad enough that i have to write something like that).

Classic:

T1 (Onyxia, MC, World Bosses): Tank & Spank. It was the Core Element in this Tier therefore it was vital to not let the Tanks die so take as much healers as possible. To some degree it also introduced Hunter Pulls which was even more important in T2.
T2 (BWL): Line of Sight, dispell everything, Aggo and Fear. The usage of line of sight was introduced and was a Core mechanic for most of the bosses in BWL. Fear required your Tanks to learn Stance dance (i know Magmadar also had fear but could also be killed with feared tanks while Nefarian would wipe you), Chromaggus still is THE dispell (and line of sight) Boss till today and healers had to adjust their interface to see debuffs or get decursive. Moreover you always had to watch for your aggro from this point until end of wotlk or something like that because most bosses were not tauntable and had aggroreduces on tanks.
T2,5 (AQ40): Enrage, Positioning and Magic-Resistance. For the first time it was actually important what your Damage Dealer did. While you could heal dead all bosses before some bosses now got a lot easier if you had good DPS (Fankriss), had tight enrages (Huhuran) or a berserk (Twins). Cthun also was a DPS Check if you didnt want to get overrun by tentacles. Also it was now a key element for all raiders to farm Resistance Gear while it before was mainly a thing for Tanks. Cthun P1 introduced the need to make exact positions for every raidmember but other bosses needed fix positions too.
T3 (Naxx40): Individual Responsibility and Gearchecks. Basically for the first time all raiders had to prepare Bossfights carefully because if you didnt know what to do in certain situations you would die and maybe even kill the Raid. Best examples are Thaddius, Heigan and Sapphiron where you would simply die if you didnt run with polarity, didnt know the Heigan Dance or didnt run behind the Ice Blocks. Moreover some bosses had Voidzones as big elements of the fight meaning if you didnt react you died. With Patchwerk you had the first pure gearcheck, if you didnt have enough DPS, HPS or Tanks without enough gear you would have no chance.

TBC:
T4 (Karazhan, Gruul, Outdoor): Not only Warriors are Tanks, Bloodlust and spreading the Raid. It was just indirectly because of the content but for the first time Feral Druids were really viable tanks, we also got the first encounter where Ranged Classes could tank Bosses! Gruul was about spreading out properly. You also had the first real Raid-CD with Bloodlust.
T5 (SSC, TK): You are the bomb! and handling Adds. While we already had "Bomb" Encounters before like Geddon Solarian brought it to the next level. Pretty much all fights had adds and because the Trash was so hard you had to learn to CC and handle all kinds of Adds. Not that there havent been adds before, but it was a core element of the instances.
T6 (MH, BT): Dont stand in the Fire! There were some more mechanics and its not the first time with ground effects. But for example Archimonde was THE "Dont stand in the Fire" Boss.
T6,5 (Sunwell): Groupheals. While Chainheal was important before being able to effectively Groupheal was more important than ever and you wanted to stack up as much as possible to outheal Raid-DMG. DPS was also very important but this was no really new mechanic...

Wotlk:
T7 (Naxx25, Malygos, Sat): Choose your difficulty and Achievements. Sartharion was the first boss with a Hardmode. The content was also designed with Achievements being the "competitive content" but it failed miserably.
T8 (Ulduar): Hardmodes, Secondary Resource Bar, Mimiron and Vehicle Fights. The first Instance designed around Hardmodes, for Yogg-Saron you had an additional Resource Bar (Insanity) which was often used again in other raids. Also the first and only pure vehicle Fight. Mimiron HC is still a reference for all those "Mimiron 2.0"-Fights
T9 (TotC): Limited Attempts. Explains itself doesnt it? Used in ICC too but then abaddoned.
T10 (ICC): Healer-Boss and unrecoverable deaths. Valithria was the first Boss that had to be healed full instead of killed, also an element often used again in other raids. As it wasnt bad enough if you died in a voidzone or due to a mechanic, you could now also die without being Rezz-able (Lich King!).

Cata:
T11 (BWD, BoT): Healingzones, Raid-CDs and DMG/Heal Hybrids. Every Healer now had his "Healingzone" where you had to stand in for effective healing, so from this point on stacking your raid always meant a lot more healing. Raid CDs were present in Wotlk too, but now a lot more classes got them and it was way more important to properly use them (Aura MAstery, Tranq, Spirit link, etc). Disc Priests being able to heal by dealing DMG is a design that has a big impact on bossfights until today.
T12 (Firelands): Basically everything that was used on Ragnaros HC. Additional HC Phases, "Kite the Boss into xy", Adds that arent allowed to reach a destination, World in Flames-Mechanic, etc.
T13 (Dragonsoul): Extra Action Button, Voidzones you have to stand in and choose how the fight goes. Our dear friend Extra Action Button had its first appearance. Voidzone you have to soak werent completely knew i think but now really important until today. Yorsahj and Madness introduced ways you can change what mechanics bosses use (choosing colors and what plattform to start on Madwing), what will still have in MoP like Protectors or Siegecrafter.

MoP:
T14 (MV, HoF, ToeS): "Throw the Ball" on Sha of Fear HC.
T15 (ToT): Healing-Absorb-Fights like Tortos. Dark Animus was kinda unique Encounter but dont know how to call his "mechanic", pretty sure we will see something like that again.
T16 (SoO): "Minigames" in Bossfights. Solo-Proving Ground at Norushen, Pacman at Sha of Pride, Assembly Line at Siegecrafter. Nothing gamechanging but i'm sure we will see more of this in the future.

Pretty sure i forgot some things but in the end these are only elements that still have effects on raiding nowadays or at least had it for a long time.

Throw the Ball --> Lady Vash'j
Minigames --> this guy in BT, where you died and had to stun/damage the zombie souls

Mechanics repeat, that's ok. But the complexity that comes with each tier feels a little bit too much.
While ICC25 was no problem with an ad-hoc random 25 raid until prof, today an ad-hoc random 25 raid would not be able to kill more than the first 2 bosses.
Or is it just my server with low-quality ppl?

I believe 'tank&spank' can be written to 99% of ALL the bosses up to 5.4.
Now, how you define 'tank&spank' that is a whole different story.

Originally Posted by Liebchen

Classic:
T2 (BWL): Line of Sight, dispell everything, Aggo and Fear. Fear required your Tanks to learn Stance dance (i know Magmadar also had fear but could also be killed with feared tanks while Nefarian would wipe you fear was introduced in Onyxia fight, when feared tank would be dead raid due to fire breath), Chromaggus still is THE dispell (and line of sight) Boss till today (You had to dispell in MC) and healers had to adjust their interface to see debuffs or get decursive. Moreover you always had to watch for your aggro from this point until end of wotlk or something like that because most bosses were not tauntable and had aggroreduces on tanks (Overaggroing on Onyxia would HURT the raid real bad).T3 (AQ40): Different kill order gives different abilities to bosses (correct me if I'm wrong)T3 (AQ20): The AQ20 brought more new mechanics. The 'bring the boss near eggs then kill eggs to damage boss', the 'one person dies if boss reaches him', the 'this massive area is for boss fight', the 'drain mana from boss or you wipe'T3 (Zul'Gurub): everything mixed up with the 5man remake >.< and a bunch of memory holes since I can hardly remember the old ZG

TBC:
T4 (Karazhan, Gruul, Outdoor): Not only Warriors are Tanks, Bloodlust and spreading the Raid. It was just indirectly because of the content but for the first time Feral Druids were really viable tanks, we also got the first encounter where Ranged Classes could tank Bosses! Gruul was about spreading out properly (you had to do that in MC). You also had the first real Raid-CD with Bloodlust (how does raid CD qualify as new raid mechanic?).You seem to have forgotten Karazhan, chess event, opera event (randomized boss), Shade of Aran - 'DO NOT MOVE', Netherspite - had to manage 4 beams and rotate people for them. Prince - whole raid goes to 1hp?
T5 (SSC, TK): You are the bomb! and handling Adds. While we already had "Bomb" Encounters before like Geddon Solarian brought it to the next level. Pretty much all fights had adds and because the Trash was so hard you had to learn to CC and handle all kinds of Adds (only 4 bosses in MC didn't have adds). Not that there havent been adds before, but it was a core element of the instances (Thats what made TBC dungeons hard, imho).SSC first boss - had to drag him through beams, never seen before. Fight in 'water', also having to fish for boss.
T6 (MH, BT): Dont stand in the Fire! There were some more mechanics and its not the first time with ground effects. But for example Archimonde was THE "Dont stand in the Fire" Boss. (Prince in Kara.)BT: Reliquary of Souls. Also, bringing Illidan into a trap (I think nothing like that was done before)Wasn't T6 when NPC's started helping us in Fights?
T6,5 (Sunwell): Groupheals. While Chainheal was important before being able to effectively Groupheal was more important than ever and you wanted to stack up as much as possible to outheal Raid-DMG. DPS was also very important but this was no really new mechanic... (going into portal to fight another boss was introduced in SWP. Also turning into a dragon and using skills? I guess Naxx did it first with proffesor, though.)

Wotlk:
T7 (Malygos, Sart): Choose your difficulty and Achievements. Sartharion was the first boss with a Hardmode. The content was also designed with Achievements being the "competitive content" but it failed miserably (In what way did achievements failed? I think they served their intended purpose: look at my E-peen everyone). Maly: wasn't it the first fight 'run into the bubble or you die' type? I believe it was the first fight to have flying targets?
T8 (Ulduar): Hardmodes, Secondary Resource Bar, Mimiron and Vehicle Fights. The first Instance designed around Hardmodes, for Yogg-Saron you had an additional Resource Bar (Insanity) which was often used again in other raids. Also the first and only pure vehicle Fight (Chess Event in Kara). Mimiron HC is still a reference for all those "Mimiron 2.0"-Fights (never heard that reference before, can you list them?)More in Ulduar: Kologarn (only similar 'remake' was Deathwing, to a lesser extent.)
T9 (TotC): Limited Attempts. Explains itself doesnt it? Used in ICC too but then abaddoned. Not sure how that qualifies as mechanic?
T10 (ICC): Healer-Boss and unrecoverable deaths. Valithria was the first Boss that had to be healed full instead of killed, also an element often used again in other raids. As it wasnt bad enough if you died in a voidzone or due to a mechanic, you could now also die without being Rezz-able (Lich King!).

MoP:T14 (Heart of Fear): Garalon and that boss where you have to run against wind.
T15 (ToT): Healing-Absorb-Fights like Tortos (I don't know what you mean here). Dark Animus was kinda unique Encounter but dont know how to call his "mechanic", pretty sure we will see something like that again. (I would compare Animus fight slightly to Omnotron system)

T16 (SoO): "Minigames" in Bossfights. Pacman at Sha of Pride (is that on normal/hc only? if not then I don't know what you mean).

T1 (Onyxia, MC, World Bosses): Tank & Spank. It was the Core Element in this Tier therefore it was vital to not let the Tanks die so take as much healers as possible. To some degree it also introduced Hunter Pulls which was even more important in T2.

Sorry, but writing MC off like this is very silly. It introduced us to group healing, dispelling entire raids, positioning adds (looking at you sulf), out ranging abilities (fear), bomb (geddon), mass CC (garr), and off tanking (golemagg), assist training (domo) and add phases with spread out positioning (rag).

Yes, world bosses were kind of a joke, but they weren't meant for guilds, it was all pugs. Even then, bosses had some mechanics that could rape (emeriss/lethon). Other bosses were all piñatas.

Sorry, but writing MC off like this is very silly. It introduced us to group healing, dispelling entire raids, positioning adds (looking at you sulf), out ranging abilities (fear), bomb (geddon), mass CC (garr), and off tanking (golemagg), assist training (domo) and add phases with spread out positioning (rag).

Yes, world bosses were kind of a joke, but they weren't meant for guilds, it was all pugs. Even then, bosses had some mechanics that could rape (emeriss/lethon). Other bosses were all piñatas.

Onyxia: Introduced a multi-phase encounter with distinct phases (might have been done in dungeons but ignoring 5-mans at this point) as well as introduced dealing with fear mechanics, first "dragon" boss with tail whip and frontal cone

Molten Core
Lucifron: Dispel mechanic
Magmadar: Dispelling enrage effects, also get out of fire
Garr: CCing raid boss adds
Baron Geddon: Really enforced group positioning as well as "you are the bomb" mechanic
Shazzrah: Maybe the first "stack now spread" type boss, not sure
Golemagg: Unkillable adds and my guess at time of progression was that this was supposed to be the gearcheck DPS race boss but kind of failed as he was a pushover, also might have been the first boss to have an undispellable enrage at low HP
Sulfuron: Interrupt the heal mechanic
Majordomo: Might be the first where you ignore boss and only kill adds to finish encounter
Ragnaros: Wow, lot of new mechanics here. Aggro reducing ability for those in melee, knockbacks, environment that damages you (don't end up in lava), might be the first tank DoT (have to check on that), a boss that is unable to move and has an attack if no one is in melee, a durability loss mechanic, and the first boss that really required resistance gear, might be first tank swap fight

BWL
Razoregore: First vehicle fight, interacting with the environment to change phases (destruction of eggs), kiting actually being intentional
Vaelstrasz: Hard Enrage, a buff that interacts with a player's resource, a non-avoidable death mechanic
Broodlord: First gauntlet boss, aggro reduction had already been in place as a mechanic but this was the first boss where that was the "main" mechanic
Flamegor: stacking debuff that can be LoSed.
Ebonroc: Healing mechanic which is dealt with through tank swaps
Firemaw: no new mechanics which made this guy a joke
Chromaggus: intentionally having an item which was used to dispel yourself
Nefarian: Having class calls (super cool) and resurrection of mobs previously killed in the encounter

AQ40
Skeram: Mirror mechanic aka gotta find the real one
Kri, Yauj, Vem: Order of killing mobs affects loot received
Satura: maybe first whirlwind mechanic?
Fankriss: first port+root mechanic
Viscidus: Using a certain school of magic to trigger a different phase of the fight
Huhuran: Enrage plus heavy nature resistance, no new mechanics but just a pain in the ass
Twin Emps: using a lock tank, having bosses that heal each other if brought near each other, having a boss immune to either physical or magic damage, having the raid split up into "teams"
Ouro: a ground rupture from the submerge
C'thun: First boss with rotating death beam, chain that increases in damage, first boss that really required range check addons, being ported to a different environment

Naxxramas
Anub'Rekhan: first boss that is required to be kited
Faerlina: killing mobs to dispel an enrage
Maexxna: Webwrap mechanic, and a raid-wide incapacitate requiring hots
Noth: Regular dispel, add control fight but just difficult
Heigan: Dance mechanic
Loatheb: Healing caused a debuff which required a healing chain, add which when killed granted a buff, possible first boss to require individual pot/cooldown rotation
Patchwerk: First boss with the only damage occurring on the tanks, an attack based on current HP of enemy in melee range
Grobbulus: Puddles which don't disappear which require slow, deliberate moving of a boss
Gluth: first raid-wide HP reducing ability, maybe first boss where he can "eat" adds
Thaddius: Having negative/positive buffs where being with opposite will deal damage and being with same will buff you
Razuvious: First boss to utilize a priest's mind control mechanic
Gothik: Splitting up the raid had been done before but this was a "hard" split as in the two sides couldn't mix once the fight had started until the end, introduced having waves of adds that increase in difficulty as well as utilizing shackles on a boss fight, also introduced the mechanic of killing mobs once spawns them again on a different side
Four Horsemen: Stacking unique debuff which is applied through LoS but can be outranged, shield-wall on a boss, meteor had been used on AQ trash but this was first time on a boss, first introduction of the void zone (very bugged and wouldn't show up half the time)
Sapphiron: using iceblocks to LoS a boss ability
KT: Charming players

Onyxia: Introduced a multi-phase encounter with distinct phases (might have been done in dungeons but ignoring 5-mans at this point) as well as introduced dealing with fear mechanics, first "dragon" boss with tail whip and frontal cone

Molten Core
Lucifron: Dispel mechanic
Magmadar: Dispelling enrage effects, also get out of fire
Garr: CCing raid boss adds
Baron Geddon: Really enforced group positioning as well as "you are the bomb" mechanic
Shazzrah: Maybe the first "stack now spread" type boss, not sure
Golemagg: Unkillable adds and my guess at time of progression was that this was supposed to be the gearcheck DPS race boss but kind of failed as he was a pushover, also might have been the first boss to have an undispellable enrage at low HP
Sulfuron: Interrupt the heal mechanic
Majordomo: Might be the first where you ignore boss and only kill adds to finish encounter
Ragnaros: Wow, lot of new mechanics here. Aggro reducing ability for those in melee, knockbacks, environment that damages you (don't end up in lava), might be the first tank DoT (have to check on that), a boss that is unable to move and has an attack if no one is in melee, a durability loss mechanic, and the first boss that really required resistance gear, might be first tank swap fight

BWL
Razoregore: First vehicle fight, interacting with the environment to change phases (destruction of eggs), kiting actually being intentional
Vaelstrasz: Hard Enrage, a buff that interacts with a player's resource, a non-avoidable death mechanic
Broodlord: First gauntlet boss, aggro reduction had already been in place as a mechanic but this was the first boss where that was the "main" mechanic
Flamegor: stacking debuff that can be LoSed.
Ebonroc: Healing mechanic which is dealt with through tank swaps
Firemaw: no new mechanics which made this guy a joke
Chromaggus: intentionally having an item which was used to dispel yourself
Nefarian: Having class calls (super cool) and resurrection of mobs previously killed in the encounter

AQ40
Skeram: Mirror mechanic aka gotta find the real one
Kri, Yauj, Vem: Order of killing mobs affects loot received
Satura: maybe first whirlwind mechanic?
Fankriss: first port+root mechanic
Viscidus: Using a certain school of magic to trigger a different phase of the fight
Huhuran: Enrage plus heavy nature resistance, no new mechanics but just a pain in the ass
Twin Emps: using a lock tank, having bosses that heal each other if brought near each other, having a boss immune to either physical or magic damage, having the raid split up into "teams"
Ouro: a ground rupture from the submerge
C'thun: First boss with rotating death beam, chain that increases in damage, first boss that really required range check addons, being ported to a different environment

Naxxramas
Anub'Rekhan: first boss that is required to be kited
Faerlina: killing mobs to dispel an enrage
Maexxna: Webwrap mechanic, and a raid-wide incapacitate requiring hots
Noth: Regular dispel, add control fight but just difficult
Heigan: Dance mechanic
Loatheb: Healing caused a debuff which required a healing chain, add which when killed granted a buff, possible first boss to require individual pot/cooldown rotation
Patchwerk: First boss with the only damage occurring on the tanks, an attack based on current HP of enemy in melee range
Grobbulus: Puddles which don't disappear which require slow, deliberate moving of a boss
Gluth: first raid-wide HP reducing ability, maybe first boss where he can "eat" adds
Thaddius: Having negative/positive buffs where being with opposite will deal damage and being with same will buff you
Razuvious: First boss to utilize a priest's mind control mechanic
Gothik: Splitting up the raid had been done before but this was a "hard" split as in the two sides couldn't mix once the fight had started until the end, introduced having waves of adds that increase in difficulty as well as utilizing shackles on a boss fight, also introduced the mechanic of killing mobs once spawns them again on a different side
Four Horsemen: Stacking unique debuff which is applied through LoS but can be outranged, shield-wall on a boss, meteor had been used on AQ trash but this was first time on a boss, first introduction of the void zone (very bugged and wouldn't show up half the time)
Sapphiron: using iceblocks to LoS a boss ability
KT: Charming players

Exactly what I wanted to say but was too lazy to point it out. For viscidus though there was also the quick mini glob add phase, you really had to be on point with your group on whatever add you were assigned. KT also had the first soft enrage due to adds, and an unforgiving interrupt rotation. You also got firemaw/flamegore mixed up (flamegore actually needed a tranq while firemaw had the crazy aoe).

Those pesky vehicle phases in Wrath fights alone disprove BC being the last bastion of originality - albeit they are a sort of intervention within a fight to provide said mechanics. Then again, there was also Razorgore and even Kil'jaeden (admittedly, that was supposed to be in a Wrath raid) - but the mechanics between each are separate entities. (3D Aerial targeting/combat in Ulduar was possibly the most innovative, sadly)

Cataclysm may have been the introduction of the most mechanics which gave the illusion of choice/(helped you not get screwed if, say, a non-rogue had to kite fire), and therefore had to try to limit their exploitation. Unfortunately, they were mostly superficial.
-Controlling Atramades' kiting phase - can't use too many gongs. Sound bar in general.
-Controlling add releases on Maloriak.
-Triage healing on Chimaeron as an actual mechanic, and not the old school taboo on over healing.
-As opposed to vehicles... Actual 3D fighting on Al'akir (not just Kael'thas's gravity reversal)?
-Steering Rhyolith in Firelands.
-Controlling Staghelm's druid phases
-Picking your poison on Yor'sahj? (There's gotta be something about this that's present somewhere else, since even the OP mentioned it)

While Cata was about choice, due to the homogenization of many class specialties in some aspect, Mists was the progression toward Personal Responsibility on top of that.
-Also, that Animus fight looks nothing like Omnotron. Omnotron was closer to a council fight than Animus was to it.

The OP brought up some of the most iconic mechanics, but like someone else pointed out, things were richer even in Molten Core. But of course, whoever raided in the BC and reads 'spreading the raid', will instantly recall the voice of his raid leader calling: 'Spread!'

I think you misunderstand the list, i didn't want to write down what exactly happened at each Boss, i rather wanted to break it down to as few as possible new/core mechanics that were introduced in a raiding Tier and that have an effect maybe until today or at least for a long time. I wanted to find the most "iconic" changes that a new Tier brought.

Tank & Spank of course is present until today, but it was introduced in Tier 1 where for the first time you had the mindset of "keep the tanks alive at all cost"... DDs loosing health even had to use bandages or were ooc rezzed because healers wanted all their mana for the tanks. And of course there was Fear and Dispell before BWL but imo it was a coremechanic in the whole Tier 2 while it only played a small role in Tier 1.

"Assisting" would be a good addition to the MC Mechanics that is right...

Bloodlust and Limited attempts had a big influence on raiding at that time... with bloodlust Blizzard could design phases that probably wouldnt be beatable without such a Raid-CD and Limited attempts simply were a mechanic that made the bosses harder. Instead of bringing an additional voidzone that will bring you multiple wipes increasing the time you need to progress by a few more IDs they just made the boss harder by allowing you only few trys every week.

Throw the Ball at Vashj rather was something unique... it didnt have much impact on later bosses. With Sha of Fear they used the "idea", combined it with the Extra Action Button and made a new mechanic out of it, so Sha of Fear imo is the Iconic "Throw the Ball" Boss as they are using the Mechanic every Tier since then (Council, Fallen Protectors).

In Karazhan there were new Mechanics, yes, but imo they didnt have that much influence. Chessevent could be seen as first vehicle fight but it wasnt really, there was no vehicle mechanic in TBC it was rather mind controlling a NPC and they never made a fight like it again. Though the new minigame-mechanics together with the vehicle mechanic from wotlk and the idea of chessevent could maybe some day lead to a new mechanic.

Achievements in T7: If you played back then you know that Blizzard tryed to make Achievements the actual Raidcontent with the Instances being easy and only the Achievements bringing some difficulty because you had to play the bosses in an odd way or basically the wrong way and therefore artifically make the bosses harder. So the ACM was a "mechanic" because it told you to play bosses in a odd way even though you didnt have to to kill the boss.
Players didnt like it and thats why blizzard then brought real Hardmodes with better loot etc in the next Tiers. So the Idea of Achievements being the only raidingcontent failed.

And sorry for not finding a term for everything, english isnt my first language and i didnt want it to sound too stupid and rather described what i mean.

How was "handling adds" not in T1? Onyxia and Majordomo both had adds to handle/cc. There have been mini games in a lot of tiers. I would consider the first BWL fight a mini game. "Don't stand in the fire" has also been around since Onyxia and MC (what, the second boss dropped fire I think?).